I have a 3 month old battery, and when I went to start my car yesterday, the battery was completely dead. It would barely flash the anti theft light. It was only a few nights ago, since I drove it. It ran fine, had bright lights, and the voltage gauge was reading normal.

I charged the battery, and disconnected the ground. Then I put my multi meter between the ground cable and the negative post of the battery. With the key off its reading almost 12 volt. 11.49 ish. I pulled every fuse and relay one at a time and seen no difference in the reading. I even disconnected the relays to my electric water pump and the 40 amp back to my BAP and FPDM. I also disconnected the charge cable at the alternator

I have no idea where the draw is coming from? Possibly the main power cable to the starter or an internal short? Kinda lost on what to test next?

You need to set your voltmeter to read amperage, not volts when testing for current draw on a battery.

I know, I think I was a brain drain I think lol.

I think I must have an issue with my meter. If I check for volts between the ground cable it reads about 12, but if I put it to A-dc 20 Ma and try and get an amp reading, it reads zero. If it reads volts why wouldn't it show any amps?

Another weird thing was when I first took it out for a tonight my mileage was not showing on the dash. After half a mile it just came on. It wasn't the dashes like some people get when they're having ECU issues it was just blank.

I think I must have an issue with my meter. If I check for volts between the ground cable it reads about 12, but if I put it to A-dc 20 Ma and try and get an amp reading, it reads zero. If it reads volts why wouldn't it show any amps?

That's because you don't check amp draw in the same you check for volts, idiot.